奇怪的循环不会使用％C工作 [英] Odd loop does not work using %c

问题描述

我靠在C编程。我写了一个奇怪的循环，但同时我用％C 在 scanf（）函数无法正常工作。结果这里是code：

I am leaning C programming. I have written an odd loop but doesn't work while I use %c in scanf().
Here is the code:

#include<stdio.h>
void main()
{
    char another='y';
    int num;
    while ( another =='y')
    {
        printf("Enter a number:\t");
        scanf("%d", &num);
        printf("Sqare of %d is : %d", num, num * num);
        printf("\nWant to enter another number? y/n");
        scanf("%c", &another);
    }
}

但是，如果我用％S 在这个code，例如 scanf函数（％S，＆安培;另一人）; ，然后它工作正常。结果为什么会出现这种情况？任何想法？

But if I use %s in this code, for example scanf("%s", &another);, then it works fine.
Why does this happen? Any idea?

推荐答案

的％C 转换读取输入的下一个字符，不管它是什么。在这种情况下，你已经previously读取使用一些％d个。你必须按下回车键读取这个数字，的但的你还没有做任何事情来读取从输入流的新线。因此，当你做了％C 的转换，它读取新线从输入流（而无需等待你真正输入任何内容，因为有已投入等着被读）。

The %c conversion reads the next single character from input, regardless of what it is. In this case, you've previously read a number using %d. You had to hit the enter key for that number to be read, but you haven't done anything to read the new-line from the input stream. Therefore, when you do the %c conversion, it reads that new-line from the input stream (without waiting for you to actually enter anything, since there's already input waiting to be read).

当您使用％S ，它会跳过在任何领先的空白，以获得比空白一些其他字符。它把新线为空白，因此跨等待新线它含蓄地跳过。由于有（presumably）闲来无事等待读，进入等待你输入的东西，你显然希望。

When you use %s, it skips across any leading white-space to get some character other than white-space. It treats a new-line as white-space, so it implicitly skips across that waiting new-line. Since there's (presumably) nothing else waiting to be read, it proceeds to wait for you to enter something, as you apparently desire.

如果你想使用％C 的转换，你可以precede它与格式字符串中的空间，这也将在任何涂白跳过流中的空间。

If you want to use %c for the conversion, you could precede it with a space in the format string, which will also skip across any white-space in the stream.

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